Cushion and cover compositions for v-belts



United States Patent 3,541,872 CUSHION AND COVER COMPOSITIONS FOR V-BELTS Sidney R. Fix, Stanley W. Olson, and John C. Wolfe, Lincoln, Nebr., assignors to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Filed Feb. 6, 1968, Ser. No. 703,248 Int. Cl. F16g 5/04; C08d 13/00 US. Cl. 74-231 9 Claims ABSTRACT OF THE DISCLOSURE V-bolts containing cushion compositions and/or elastomeric impregnated fabric envelopes which contain polyfluorohydrocarbon resins which increase the resistance to failure due to flexing of said V-belts.

This invention relates to cushion stocks for V-belts, elastomeric impregnated fabric envelopes for V-belts, V- belts containing said cushion stocks and fabric envelopes, and a process for improving the resistance to failure due to flexing of said V-belts.

In the art of power transmission V-belts characterized by a cross section in the form of a trapezoid or truncated V which wedgingly engages the similarly shaped peripheral groove of a V-pulley are employed in an ever increasing number of applications. A primary reason for this popularity is the improved load carrying and power transmitting capability afforded by the forced contact between the sides of the belt and the sides of the pulley groove Whhich resist slippage of the belt in the pulley. These well known belts are normally characterized by such basic elements as a tension member composed of a rubber insulated cord layer, and a compression (cushion) section. An example of a belt of this type is described and illustrated (FIG. 3) in US. Pat. 3,051,212. Often the belt is covered by a rubberized fabric envelope which covers the'entire surface of the belt. An example of such an envelope is discussed and shown in US. Pat. 3,260,126. In other instances no envelope is used, resulting in what is commonly known as a molded or raw edge belt. As a result of the severe operating conditions to which V-belts are often subjected the resistance of the belts to failure due to flexing has become increasingly important. In addition, where the cushion section of the belt is not covered by a rubberized fabric the surface of the cushion after vulcanization can possess imperfections which not only detract from the appearance of the cushion section, but in addition, provide sites for flex cracking and other forms of deterioration to occur. It is therefore desirable to improve the performance and appearance of V-belts. It is desirable that the resistance to failure due to flexing be improved. Such failure can take the form of a delamination of the elements of the belt and cord separation. Increased abrasion resistance is also desirable. It is also desirable to provide cushion sections with less surface imperfections in order to improve the appearance of the surface of the cushion stock and also to aid in preventing flex cracking and other forms of deterioration.

It is an object of the present invention to provide V- belts with improved resistance to failure due to flexing and improved abrasion resistance, cushion stocks and elastomeric impregnated fabric envelopes (fabric covers) which will aid in providing said V-belts with improved resistance to failure due to flexing and aid in providing improved abrasion resistance, and a process for improving the resistance to failure due to flexing and to improve the abrasion resistance of V-belts.

Some of the objects of the present invention are accomplished by blending a carbon black loaded composition comprising (A) 100 parts by weight of at least one p CC elastomeric compound comprising (1) from about 50 to 100 parts by weight per 100 parts by weight of the elastomeric compound of polychloroprene and (2) from 0 to about 50 parts by weight per 100 parts by weight of the elastomeric compound of at least one rubbery diene polymer, (B) from about 0 to about parts by weight per parts by weight of the elastomeric compound of at least one flexible filamentary material and (C) from about 0.5 to about 20.0 parts by weight per 100 parts by weight of the elastomeric compound of at least one polyfluorohydrocarbon resin and then building a V-belt using the above composition to form the cushion portion of the belt and vulcanizing said V-belt. Some objects are accomplished by impregnating fabric with the above composition to form fabric envelopes for V-belts. Other objects will appear subsequently herein.

Preferably, the elastomeric compound consists essentially of polychloroprene, i.e., the rubbery polymer of 2- chlorobutadiene-l,3. This material is designated as ASTM D 14l856T at (C).

Rubbery diene polymers which may be used in combination with the polychloroprene include natural rubber, such as crepe rubber, and synthetic rubbers such as homopolymers of a conjugated 1,3-diene such as isoprene and butadiene, and in particular, polyisoprenes and polybutadienes having essentially all of their repeating units combined in a cis-l,4 structure; copolymers of a conjugated 1,3-diene such as isoprene and butadiene with up to 50 percent by weight of at least one copolymerizable monomer such as styrene and acr lonitrile; and polymers of monoolefins containing unsaturation, i.e., carbon to carbon double bonds, such as terpolymers of ethylene, propylene and a nonconjugated diene.

The flexible filamentary material to be used in the prac' tice of the present invention may be any flexible fiber of a shortened length which is generally used to increase the stiffness and hardness of cushion stocks. Such usage of fibers is noted in US. Pat. 3,051,212, column 4, lines 67 and 68. Well known fibers such as cotton linters and chopped or ground polyamides, such as nylons; regenerated cellulose such as rayon; and polyester fibers are exemplary of the types of the materials that may be used as flexible filamentary materials. The materials should be of such size that they can be dispersed uniformly throughout the cushion stock, and of such size to provide an increase in stiffness and hardness of the cushion stocks. Preferably from about 5 to about 30 parts b weight of the flexible filamentary material are used.

=Polyfluorohydrocarbon resins, which have polymer lubricating properties, which may be used in the practice of the present invention are essentially completely fluoronated polymers such as polytetrafluoroethylene and essentially completely fluorinated ethylene propylene copolymers such as those made by copolymerizing hexafluoropropylene and tetrafluoroethylene. Preferably from about 1.0 part to about 5.0 parts of the polyfluorohydrocarbon resin are used per 100 parts by Weight of the elastomeric compound. It is preferred that the polymers be in powdered form to facilitate ease of incorporation into the elastomers with conventional mixing equipment.

The method of combining the components of the cushion stock is not normally critical. The elastomeric compound, flexible filamentary material and polyfluorohydrocarbon resin may be mixed by such methods as Banbury mixing and open mill mixing. The components may be mixed in any order, in increments, and in any combination.

Any conventional vulcanization system may be used to vulcanize the cushion stock. When the elastomeric compound of the cushion stock consists essentially of polychloropene, materials such as zinc oxide may be used to vulcanize the cushion stock. Where diene polymers are used as a portion of the elastomeric compound it is preferred that some sulfur vulcanization system be used.

Any conventional carbon black may be used to load the cushion stock. The level of black should normally be from about 10 to about 90 parts by weight per 100 parts by weight of the elastomeric compound. A range of from about 20 to about 40 parts by weight is preferred.

The cushion stock composition may also be used to impregnate fabric to form fabric envelopes for V-belts, with the qualification that it preferably contains essentially no fiber loading. An example of a fabric envelope for a V-belt is shown in FIG. 6 and discussed at column 5, lines 26 to 28 of US. Pat. 3,260,126. The fabric may be any conventional V-belt fabric, e.g., cotton, rayon, nylon and polyesters. The fabric may be impregnated in any conventional manner, for example by swelling the elastomer in an organic solvent to form a dough-like composition, spreading the dough-like composition on the fabric and driving off the organic solvent. Said envelopes improve the resistance to failure due to flexing of V-belts.

The following examples contain illustrations of the practice of the present invention and are not intended to limit the present invention.

EXAMPLE 1 Eight V-belts, A through H, having tensile and cushion elements were fabricated using identical trapezoid type construction and vulcanized. The cushion portions of the belts were devoid of any fabric envelopes. The compounds and cords used in constructing the V-belts were the same with the exception of the cushion portion of the belts. The cushion portion of belts A through D was prepared by milling together the following formulation.

Components: Parts by weight Nonproductive polychloroprene stock 64.50 Scrap 25.00 Zinc oxide 3.50 Chopped cotton, rayon and nylon fibers 7.00

The cushion portion of belts E through H was prepared by milling together the following formulation.

Components: Parts by weight Nonproductive polychloroprene stock 45.80 Scrap 50.00 Zinc oxide 3.53 Polytetrafluoroethylene 0.67

The nonproductive polychloroprene stock contained 100 parts by weight of polychloroprene as its sole elas tomeric component, 20.0 parts of PEP carbon black, magnesium dioxide, processing oil, stearic acid, phenylbetanaphthylamine and phenylalphanaphthylamine.

The scrap was unvulcanized productive V-belt scrap which had been ground into fine particles. The scrap V- belts were similar to belts A through. H regarding both construction and composition. However, the cushion portion did not contain polytetrafiuoroethylene. The insulation portion of the V-belt scrap comprised approximately 20 percent by weight of the V-belt scrap. The polyester cord comprised about 5 percent by weight. The cushion portion comprised about 75 percent by weight. The insulation portion contained 100 parts by weight of polychloroprene as its sole elastomeric component, 20.0 parts of PEP black, 10.0 parts of cotton linters, reinforcing silica, magnesium oxide, processing oil, stearic acid, zinc oxide, a polyethylene wax releasing agent and phenylalphanaphthylamine.

As mentioned above, the cushion portion of the V- belt scrap had approximately the same composition as the cushion stocks of belts A to H. The cushion stocks in belts A to H were essentially the same, containing approximately 15 percent by weight of chopped fiber,

with the exception that the cushion portion of belts E to H contained polytetrafluoroethylene and the cushion portions of belts A to D contained no polytetrafiuoroethylene. Both sets of belts contained a tensile portion comprised of polyester cords insulated by an elastomeric formulation similar to the insulation composition described earlier herein.

EXAM PLE' 2 Cushion stocks for V-belts within the scope of the present invention are also prepared by mixing the fol lowing compounds on an open mill.

Components: Parts by weight Polychloroprene 100.0

Carbon black (FEF) 30.0 Magnesium oxide 2.0 Processing oil 7.5 Amine antioxidant 0.50 Stearic acid 1.0 Wax 2.0 Cotton linters 15.00 Polytetrafluoroethylene 2.00 Zinc oxide 4.00

Chopped or ground rayon, nylon and polyester fibers are interchangeable with cotton linters. Other essentially completely fiuoronated polyfluorohydrocarbon resins such as essentially completely fluoronated ethylene propoylene copolymers are also interchangeable With polytetrafiuoroethylene.

EXAMPLE 3 The belts of Example 1 were dynamically tested on a pulley arrangement according to SAE procedure I637 (SAE Handbook, 1967 edition) at 13 horsepower with the exception that the small pulley was 2.5 inches in di ameter. The time to first failure as indicated by the first parting of any of the elements of the belt from the rest of the belt was recorded.

Tingle to a ure Belt Condition of belt at failure (hours) A Components separated at cordiine, top 159 fabric came off. B Top fabric came 01f, edge cord came out 166 side of belt. 0 Top fabric came ofi, edge cord came 238 outside of belt. D Cushion section delaminated from rest 246 of belt.

Average 202 E Delamination of insulation to cordllne... 369 F-.. Severe delamination at cordline 136 Delamination at cordline 366 Edge cord broke out side of belt, delami- 256 nation at cordline.

Average 282 As shown by the above data the belts possessing a cushion within the scope of the present invention (belts E to H) possessed a resistance to failure due to flexing which was superior to the resistance of belts outside the scope of the present invention (belts A to D).

The surfaces of the cushion portions of belts A to D also contained some surface imperfections, whereas the surfaces of the cushion portions of belts E to H contained no appreciable surface imperfections.

The belts tested in Example 3 did not possess a fabric envelope surrounding the cushion element. Tests, however, have been run with belts containing a cushion element surrounded by a fabric envelope. The cushion element contained polytetrafiuoroethylene. These belts also showed improved resistance to failure due to flexing. The use of polyfluorohydrocarbon resins also enhances the abrasion resistance of the cushion stocks.

EXAMPLE 4 Eight V-belts (I through P) were constructed in essentially the same fashion as the belts A to D described in Example 1 and vulcanized. The composition of the elements was similar to the composition of the elements of belts A to D. The construction of the belts differed in that each belt contained a fabric envelope (cotton/nylon blend) impregnated with a black loaded (50 parts by weight of black) productive polychloroprene stock. The fabric was impregnated by swelling the polychloroprene composition with an organic solvent to form a dough-like composition, spreading the dough-like composition on the fabric and driving off the solvent. The cushion stock of these eight belts did not contain fiber loading. Four belts (M to P) contained polytetrafluoroethylene in the polychloroprene portion of the fabric envelope, also known as a fabric cover. The other four belts (I through L) contained no polytetrafluoroethylene in the fabric envelope. The belts were tested in a manner similar to that described in Example 3 using a 2,5 idler pulley, a tension of 140 pounds and 14 horsepower.

As shown by the above data, belts M through P of the present invention were superior in performance.

The use of polyfluorohydrocarbon resins also enhances the abrasion resistance of the fabric envelopes.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What we claim is:

1. In a transmission belt having a tension element therein and including at least one flexing portion containing a carbon composition, the improvement wherein the loaded composition of at least one of said portions is comprised of (A) 100 parts of at least one elastomeric compound having (1) from about 50 to 100 parts of polychloroprene and (2) from about to about 50 parts of a different rubbery diene polymer, (B) from about 0 to about 75 parts of at least one flexible filamentary ma- 6 terial, (C) from about 0.5 to about 20.0 parts of at least one polyfluorohydrocarbon resin, and (D) from about 10 to about parts of carbon black, said parts being by weight per parts of elastomeric compound.

2. The improvement according to claim 1 wherein at least one of the flexing portions is a compression element disposed within the belt and is at least substantially formed from said composition.

3. The improvement according to claim 1 wherein at least one of the flexing portions is a fabric cover element which at least substantially forms the outer periphery of the belt and is impregnated with said composition and said composition has about 0 part of the flexible filamentary material.

4. The improvement according to claim 1 wherein the elastomeric compound consists essentially of polychloroprene.

5. The improvement according to claim 1 wherein the flexible filamentary material is selected from the group consisting of a polyamide, regenerated cellulose, polyester and cotton.

6. The improvement according to claim 1 wherein the polyfluorohydrocarbon resin is at least one resin selected from the group consisting of polytetrafluoroethylene and essentially completely fluoronated ethylene Propylene copolymer resins.

7. The improvement according to claim 1 wherein the polyfluorohydrocarbon resin is polytetrafluoroethylene.

8. The improvement according to claim 1 wherein the amount of polyfluorohydrocarbon resin is from about 1.0 to about 5.0 parts.

9. A process for improving the flex life of a transmission belt having a tension element therein and including at least one flexing portion containing an elastomeric composition, comprising the step of forming at least one of the flexing portions from the elastomeric composition of claim 1.

References Cited UNITED STATES PATENTS 2,631,463 3/ 1953 Waugh 74233 3,002,938 10/ 1961 Gagne 260-890 3,011,221 12/1961 Howell 260890 3,223,676 12/1965 Rucker 260890 WILLIAM SHORT, Primary Examiner E. H. NIELSEN, Assistant Examiner US. Cl. X.R. 74-233; 26017.4

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5l 1,872 Dated November 21. 1970 Inventor(s) Sidney R Fix, Stanley W Olson and John C Wolfe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, Column 5, line 2 1;, after "oerbon" insert --black loaded--;

line 145, delete "loaded".

Signed and sealed this 6th day of April 1971.

(SEAL) Attest:

EDWARD M.FLEI'GHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

